There has been known a substrate cleaning apparatus for cleaning a surface of a substrate, such as a wafer, by pressing a cylindrical roll cleaning member against the substrate. This type of substrate cleaning apparatus is provided with a roll arm that rotatably supports the roll cleaning member. This roll arm is coupled to an elevating mechanism for moving the roll cleaning member closer to and away from the surface of the wafer. This elevating mechanism is disposed beside the roll arm because of an issue of a layout space. The elevating mechanism includes a horizontally-extending support arm, which supports the roll arm.
In this structure that supports the roll arm with the horizontally-extending support arm, a self-weight of the roll arm is applied to the support arm at all times. As a result, wear and permanent strain (or creep) may occur in components constituting the support arm, possibly causing a change in height of the roll cleaning member, supported by the roll arm, from an initial set position.
Thus, a height-adjustment mechanism for adjusting the height of the roll cleaning member is installed on the roll arm. FIG. 10 is schematic cross-sectional view of a conventional height-adjustment mechanism. As shown in FIG. 10, in this height-adjustment mechanism, two wedges 180, 181, each having a cross section of an approximately right-angled triangle shape, are overlapped one above the other such that their inclined surfaces contact each other. A height of a roll cleaning member 146 can be adjusted by regulating an amount of overlapping of these wedges 180, 181. In this height-adjustment mechanism, an adjustment screw 183 for regulating the amount of overlapping of the wedges 180, 181 is mounted to the lower wedge 181. The adjustment screw 183 is rotatably supported by a screw support 184 that is fixed to the roll arm 185. This screw support 184 allows the adjustment screw 183 to rotate about its own axis, while preventing the adjustment screw 183 from moving in a horizontal direction.
When the roll cleaning member 146 is to be elevated, the adjustment screw 183 is rotated in a clockwise direction to move the lower wedge 181 to a right side in the drawing, so that a relative distance between the upper wedge 180 and the lower wedge 181 is decreased. On the other hand, when the roll cleaning member 146 is to be lowered, the adjustment screw 183 is rotated in a counterclockwise direction to move the lower wedge 181 to a left side in the drawing, so that the relative distance between the upper wedge 180 and the lower wedge 181 is increased.
The height-adjustment mechanism having the above structures is provided on the roll arm, and is located right above a center of the roll cleaning member. This location is an optimal location for measuring a pressing load (i.e., a load at which the roll cleaning member presses the substrate). However, it is difficult to install a load-measuring device, such as a load cell, at this optimal location, because there exists the height-adjustment mechanism.
Furthermore, an amount of adjustment of the height-adjustment mechanism shown in this drawing is approximately plus and minus 1 mm, which is insufficient to adjust the height of the roll cleaning member 146. In order to increase the amount of adjustment, it is necessary either to increase an angle of the inclined surfaces of the wedges 180, 181 with respect to the horizontal direction, or to enlarge a size of the wedges 180, 181. However, in the case of increasing the angle of the inclined surfaces, a greater power is required for sliding the wedges 180, 181 in the horizontal direction. Therefore, it is difficult to conduct such a design change. Increasing the size of wedges 180, 181 entails a larger installation space.
Furthermore, in the conventional height-adjustment mechanism, the adjustment screw 183 for sliding the wedges 180, 181 protrudes horizontally from the roll arm 185. In such a construction, a processing liquid, such as a chemical liquid, rinsing liquid, or the like, which is used for cleaning the substrate, may adhere to the adjustment screw 183. In such a case, the attached processing liquid may drop onto the surface of the substrate, possibly causing a back contamination of the substrate. The chemical liquid or the rinsing liquid is typically supplied onto the substrate from obliquely above the substrate with use of a chemical liquid nozzle or a rinsing liquid nozzle disposed beside the roll arm 185. However, since the adjustment screw 183 protrudes from the roll arm 185 in the horizontal direction, the chemical liquid nozzle or the rinsing liquid nozzle must be disposed so as to avoid the adjustment screw 183. Such an arrangement of the adjustment screw 183 limits a layout, such as a location or an angle, of the chemical liquid nozzle and the rinsing liquid nozzle, thus inhibiting a free layout design.